University of California

Leland Stanford Junior University

Sri International

Voltage Security, Inc.

Amit Sahai

Brent Waters

Dan Boneh

The present invention relates to a method for traitor tracing. One embodiment of a method for determining at least one traced private key used by a decoder to decrypt an encrypted message includes defining an input ciphertext, the input ciphertext being associated with a tracing private key and having a sublinear size, calling the decoder on the input ciphertext, and associating the tracing private key with a set of traced private keys if the decoder is able to correctly decrypt the encrypted message in accordance with the input ciphertext, the set of traced private keys including at least one private key.

Method and apparatus for tracing the source of decryption keys used by a decoder

Systems and methods for supporting an identity-based-encryption (IBE) scheme with partial attribute matching capabilities are provided. Plaintext may be encrypted into ciphertext using an IBE public key that is based on an attribute set w. A recipient of the ciphertext may have the attributes in an overlapping but different attribute set w'. The recipient may request an IBE private key for decrypting the ciphertext from an IBE private key generator. After verifying the recipient's credentials, the IBE private key generator may generate IBE private key components based on the recipient's attribute set w&#x2032;. The recipient may use an IBE private key SK constructed from the IBE private key components to decrypt the ciphertext. Decryption will be successful even though attribute set w&#x2032; is different from attribute set w, provided that the overlap |w&#x2229;w&#x2032;| is greater than a threshold value.

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Los Angeles, CA, United States of America

Amit Sahai